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Title
The 3rd ISPRS Workshop on Dynamic and Multi-Dimensional GIS & the 10th Annual Conference of CPGIS on Geoinformatics
Author
Chen, Jun

ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001
impossible to be presented in the GIS. These features or their
details must be eliminated. The progress is the opposite one to
the selection. The left features must to be displayed as
probably as detail depending on the purpose and scale.
Purpose
Any GIS is used for some thematic fields or purposes. In
the case, some features are very important to the users
and the others are not. For example, a GIS is used for
transportation and then the roads, even pedestrians are
important to be displayed in the GIS. Oppositely, Some
trees, windows, chimney, even the roof of the buildings
are unimportant to be display in the GIS.
• Simplification
In one word, we can not display very detail about the feature
as the scale changing smaller. In the other hand, it is
unnecessary to display so detail for certain purpose, we can
not display very detail about the feature as the scale changing
smaller. In the other hand, it is unnecessary to display so detail
for certain purpose. The third, GIS itself is a scientific and
artistic work, we must follow not only the reality but also
inputting artistic elements when we display it using the GIS
way. We must keep its position, shape, etc. correctly as
possible as we can. At the same time, we try to make the work
beautiful and easily understanding without destroying its
essential shape.
Scale
When the scale changes we can not present all the
features or their details that are necessary (scale change
smaller) or oppositely. In the case, we have to eliminate
some features or their detail that are not only
unnecessary but also very important.
• Bunching and Injoining
Bunching the features with the same characteristic and close
proximity each other together, Displaying as a feature that
presents the volume, fill up the spaces among them and
average (e.g. highest or lowest) high.
There are two main reasons we use bunching for
generalization:
o The features are too small to be display as the real
shape. We use bunching to show that there are
features in the space and tell the reader the extent of
the space.
o We do not need to display these features one by one.
• Displacement
Detecting feature conflicts, removing the less important
conflicting features, adjusting feature extents to satisfy the
threshold of separation and keeping the relationship. In the
example, the building has been removed to maintain the
relationship between the road and the building when the read
was exaggerated.
• Exaggeration
Increasing the spatial extent of a feature representation for the
purpose of emphasis and legibility; for example, enlarging the
high of a chimney and the size of the door of the example
building, which are the main parts of the building. The chimney
will be the obvious object for drivers, the traffic light is very
important object for the transportation system.
CONCLUSION AND FUTURE
In the study, the basic algorithms were given assistant with
simply examples. It is the first step for the future research, and
also these algorithms need testing under more conditions.
To enhance 3D GIS software solutions such that the users can
produce multiple-scale and multiple-subject output more
efficiently, both the semi-automation or automation digital 3D
spatial data generalization and semi-automated and
automated 3D GIS data capture in real time must be
addressed.
Urban facilities (on ground, under ground, in spatial)
generalization capability into the 3D GIS product environment
will be a challenging and main task in general usage. Special
usage such as in building structure project design in 3D or 4D
will be widely used in the future.
What does the future of generalization for 3D GIS hold?
• Short-term Plans
> Improving the algorithms of 3D GIS generalization in
more examples and conditions;
> Suitable normalization for 3D GIS products;
> Comprehensive library of standard 3D symbols and
possibility to create new ones;